Adaptable thermal management of a vehicle dual-clutch transmission

ABSTRACT

A method of managing clutch thermal loads in a multi-speed dual-clutch transmission (DCT) that is paired with an engine in a vehicle. The method includes assessing whether the vehicle is being accelerated and identifying a DCT clutch slipping during the acceleration. The method also includes determining vehicle parameters, determining an amount of time remaining for the clutch to stop slipping using the determined vehicle parameters, and determining an amount of time remaining until the clutch reaches a threshold temperature. The method additionally includes comparing the determined amount of time remaining for the clutch to stop slipping with the determined amount of time remaining until the clutch reaches the threshold temperature. Furthermore, the method includes activating an indicator if the determined amount of time remaining until the clutch reaches the threshold temperature is less than the determined amount of time remaining for the clutch to stop slipping.

TECHNICAL FIELD

The disclosure relates to a system and method employing adaptablethermal management for a multi-speed, dual-clutch transmission in avehicle.

BACKGROUND

Modern vehicles are frequently equipped with multi-speed, dual-clutchtransmissions (DCT) as part of the subject vehicle's powertrain. SuchDCTs are favored for their increased mechanical efficiency in comparisonwith typical, torque-converter equipped automatic transmissions.Additionally, DCTs are often preferred over typical automated manualtransmissions for the capability of DCTs to provide higher quality gearshifts.

A typical DCT employs two friction clutches for shifting among itsforward ratios, and accomplishes such shifts by alternating engagementbetween one and the other of the two friction clutches. Such amulti-speed, dual-clutch transmission may be utilized in a hybridvehicle, i.e., a vehicle employing two or more distinct power sources,such as an engine and an electric motor, for transmitting propulsionenergy to the subject vehicle's driven wheels.

During operation of a vehicle equipped with a DCT, significant amountsof heat or thermal loads may be generated within the DCT clutches due toclutch slip used during launching or accelerating the vehicle. When suchloads exceed specific thresholds, performance and durability of the DCTclutches, as well as general performance of the DCT and the vehicle, maybe adversely affected.

SUMMARY

A method is disclosed for managing clutch thermal loads in a multi-speeddual-clutch transmission (DCT) that is paired with an internalcombustion engine in a vehicle. The method includes assessing whetherthe vehicle is being accelerated by the engine and identifying a clutchin the DCT that is being slipped during the acceleration. The methodalso includes determining vehicle parameters indicative of an amount oftime remaining until the clutch will cease to slip, determining theamount of time remaining until the clutch will cease to slip using thedetermined vehicle parameters, and determining an amount of timeremaining until the clutch reaches a threshold temperature. The methodadditionally includes comparing the determined amount of time remaininguntil the clutch will cease to slip with the determined amount of timeremaining until the clutch reaches the threshold temperature.Furthermore, the method includes activating an indicator if thedetermined amount of time remaining until the clutch reaches thethreshold temperature is less than the determined amount of timeremaining until the clutch will cease to slip.

The threshold temperature may be indicative of the clutch beingoverheated. In such a case, the method may additionally includeregulating the operation of the DCT such that energy input to the clutchis reduced when the clutch substantially reaches the thresholdtemperature.

The act of regulating operation of the DCT such that energy input to theclutch is reduced may include disengaging the clutch.

The clutch may be in the process of being engaged in a forward gearratio of the DCT. In such a case, the clutch may cease to slip upon anupshift to another gear ratio via the other of the two clutches.

The determined vehicle parameters may include road speed andacceleration of the vehicle, and position of a vehicle accelerator. Thevehicle parameters may then be assembled into a DCT upshift table andprogrammed into the controller for appropriate access.

The clutch may be in the process of being engaged in a reverse gearratio of the DCT. In such a case, the clutch may cease to slip upon lockup of the clutch.

Each of the acts of assessing whether the vehicle is subject to theacceleration event, identifying the clutch in the DCT that is beingslipped during the acceleration event, determining vehicle parametersindicative of the amount of time remaining until the clutch will ceaseto slip, determining the amount of time remaining until the clutch willcease to slip, determining the amount of time remaining until the clutchreaches the threshold temperature, comparing the determined amount oftime remaining until the clutch will cease to slip with the determinedamount of time remaining until the clutch reaches the thresholdtemperature, and activating the indicator may be accomplished via acontroller.

The method may additionally include activating the indicator when theclutch substantially reaches the threshold temperature.

The indicator may be at least one of an audible signal and a visualdisplay. Additionally, the visual display may include a request for anoperator of the vehicle to at least one of i) increase speed or apply avehicle brake, and ii) apply and hold the vehicle brake. The indicatormay additionally include a coded message stored in the controller andconfigured to be retrieved on demand.

The clutch may be one of an odd-ratio clutch and an even-ratio clutch.

A vehicle having a DCT, an internal combustion engine, and thecontroller configured to manage thermal loading on the clutch in the DCTis also disclosed.

The above features and advantages, and other features and advantages ofthe present disclosure, will be readily apparent from the followingdetailed description of the embodiment(s) and best mode(s) for carryingout the described invention when taken in connection with theaccompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a vehicle powertrain having aninternal combustion engine and a dynamically-shiftable, dual-clutchtransmission (DCT).

FIG. 2 is a schematic representation of a cross-sectional view of theDCT shown in FIG. 1, specifically illustrating the transmissionclutches.

FIG. 3 is a flow chart illustrating a method of managing clutch thermalloads in the DCT depicted in FIGS. 1-2.

DETAILED DESCRIPTION

A dynamically-shiftable multi-speed dual-clutch transmission (DCT) maybe employed as part of a powertrain for a vehicle in order to furtherenhance the vehicle's efficient use of non-renewable sources of energy,such as fossil fuels. Such a DCT may be provided for a vehicle having aconventional powertrain employing solely a single internal combustionengine for powering the vehicle, or a hybrid type of a powertrain,wherein the vehicle may be powered by an engine, an electric motor, or acombination of the two.

As used herein, the term “dynamically-shiftable” relates to employing acombination of two friction clutches and several dogclutch/synchronizers to achieve “power-on” or dynamic shifts byalternating between engagement of one friction clutch and the other.Additionally, “dynamic shifting” means that drive torque is present inthe transmission when a clutched shift to an oncoming speed ratio ismade. Generally, the synchronizers are physically “pre-selected” for theoncoming ratio prior to actually making the dynamic shift. As will bereadily understood by those skilled in the art, prior to making a“dynamic shift”, synchronizers are “pre-selected” to the necessarypositions of both the oncoming and off-going ratios prior to actuallyshifting the torque path from one clutch to the other. The pre-selectcondition is postponed as long as possible to minimize spin lossesbecause pre-selecting the next ratio forces a speed difference in theopen, i.e., not engaged, clutch. This particular gear arrangement allowsthe combination of torque-transmitting mechanisms for any ratio and itsneighboring ratio (i.e., ratio N and ratio N+1) without obtaining amechanical tie-up in the transmission.

Referring to FIG. 1, a vehicle 10 having a powertrain 12 is depicted.The powertrain 12 includes an internal combustion engine 14 configuredto generate torque, drive wheels 16 configured to interface with a roadsurface, and a DCT 18 operatively connected to the engine 14 andconfigured to transmit engine torque to the drive wheels. A vehicleaccelerator 17, such as a pedal or a lever, is provided for a vehicleoperator in order to control engine power to drive the vehicle 10. Avehicle brake 19, shown as a pedal in FIG. 1, is provided for thevehicle operator in order to restrain motion of the vehicle 10. Althoughnot specifically shown, as noted above, the powertrain 12 may beconfigured as a hybrid type and additionally include an electric motor.

The engine 14 utilizes a crankshaft 15 for converting reciprocal motioninto rotational motion, as is understood by those skilled in the art.The DCT 18 is paired with the engine 14 at an engine-transmissioninterface using any appropriate means, including fasteners (not shown)such as threaded screws and dowels. The DCT 18 includes a transmissioncase 20 for housing a geartrain 22 that is configured to provide apredetermined number of selectable gear ratios for connecting the enginecrankshaft 15 to the drive wheels 16. The DCT 18 also includes acontrols subsystem 24 employed to control operation of a clutchsubsystem 26.

Although not specifically shown, the controls subsystem 24 may generallyinclude an electric drive system that is configured to convert DCcurrent of an on-board energy storage device, such as a battery, into ACcurrent for powering a three-phase electric motor. The electric motormay then be employed to drive an electric pump to pressurize a body ofcontrol fluid, such as pentosin, through a DCT valvebody that includes asystem of valves and solenoids. In turn, the DCT valvebody employs thesystem of valves and solenoids to direct the pressurized fluid toregulate operation of the clutch system 26.

As shown in FIG. 2, the clutch subsystem 26 is located inside a clutchhousing 27 and includes dry clutches 28 and 30. As shown, the clutch 28is an even-ratio clutch, and the clutch 30 is an odd-ratio clutch. Theclutches 28, 30 are configured to select the particular drive gear ratioin the DCT 18. Specifically, the clutch 28 includes a clutch plate 32having friction facings 32-1, while the clutch 30 includes a clutchplate 34 having friction facings 34-1. The DCT 18 also includes a clutchcover 36, which has a portion 38 employed to actuate the clutch 28 via aspring 40 and a portion 42 employed to actuate the clutch 30 via aspring 44. The clutch 28 also includes a pressure plate 46, while theclutch 30 includes a pressure plate 48.

Additionally, clutches 28 and 30 share a center plate 50, wherein eachof the pressure plates 46 and 48 clamp the respective friction facings32-1 and 34-1 against the center plate 50 through the action of thesprings 40 and 44 at a preselected rate to engage the respective clutch.During operation of the DCT 18, when one of the clutches 28, 30 istransmitting engine torque in any particular ratio, the other of the twoclutches pre-selects an appropriate synchronizer of the oncoming ratio.The above-described valvebody controls selective engagement of theclutches 28, 30 by directing the control fluid to various solenoids (notshown) that in turn regulate flow of the control fluid to theappropriate clutch.

During operation of the vehicle 10, when the DCT 18 is transmittingengine torque, thermal loading on the clutch subsystem 26 may becomeexcessive, i.e., one or more of the clutches 28, 30 may experience arapid temperature increase and an over-heat condition. Such thermalloading is frequently the result of clutch slip used to launch thevehicle 10 and during gear shifts of the DCT 18. Consequently, if notaddressed, such excessive thermal loading may lead to reducedperformance and durability of friction facings 32-1 and 34-1, as well asgeneral performance of the DCT 18 and the vehicle 10. What constitutesexcessive thermal loading with respect to the clutches 28, 30 may bebased on operating requirements of the DCT 18, as well as on durabilitylimits of the facings 32-1 and 34-1, as well as other components of therespective clutches.

With renewed reference to FIG. 1, the vehicle 10 also includes acontroller 52 that may be a dedicated transmission controller configuredto regulate operation of the DCT 18, or an integrated powertraincontroller configured to regulate operation of the entire powertrain 12.The controller 52 is also programmed with an algorithm and configured tomanage thermal loads on clutches 28, 30 in the DCT 18. As part of itsmanaging of the thermal loads on clutches 28, 30, the controller 52 isprogrammed to assess whether the vehicle 10 is being accelerated by theengine 14. In such a case, the engine 14 has previously been started andthe vehicle 10 has been commanded by its operator to either launch froma stop or accelerate from a roll, with the DCT 18 transmitting enginetorque to the drive wheels 16.

Additionally, the controller 52 is programmed to identify which clutchof the clutches 28 and 30 is being slipped during the accelerationevent. Such a determination is easily achieved based on the knowledge ofwhich gear has been selected in the DCT 18 during the accelerationevent. In the case when the vehicle is being launched from a stop, it ismost likely that the torque transferring and, therefore, the slippingclutch would be the odd-ratio clutch 30 while engaging first gear.However, the even-ratio clutch 28 may also be used, if it is deemeddesirable to launch the vehicle 10 in a higher, such as second, gear.The controller 52 is programmed to determine an amount of time remaininguntil the subject clutch 28 or 30 will cease to slip. The determinationfor the amount of time remaining until the subject clutch 28 or 30 willcease to slip may be based on design calculations and/or empiricallyderived data.

The controller 52 is also programmed to determine vehicle operatingparameters 54 indicative of an amount of time remaining until theslipping clutch 28 or 30 will cease to slip. Such vehicle parameters 54may include speed and acceleration data of the vehicle 10. Additionally,another one of the pertinent vehicle parameters 54 may include aposition of the accelerator 17. A particular position of the accelerator17 may be indicative of the vehicle 10 being accelerated while thesubject clutch 28 or 30 is controlled to slip in order to facilitategradual application of engine power to the drive wheels 16 and/orgradually synchronize the rotating speed of the drive wheels with thespeed of the engine 14. Accordingly, when the clutch 28 or 30 is beingengaged during vehicle launch to transmit sharply applied engine torque,and also in the process of a hand off from one gear to the next during agear change for driving the vehicle 10, the subject clutch undergoescontrolled slip. Some or all of the vehicle parameters 54 may beassembled into a DCT upshift table 56 which may then be programmed intothe controller 52 for subsequent access during operation of the vehicle10.

The subject clutch 28 or 30 may be in the process of being engaged in aforward gear ratio of the DCT 18. In such a situation, the clutch 28 or30 may cease to slip when the DCT 18 undergoes an upshift to anotherforward gear ratio via the other of the two clutches 28, 30. The subjectclutch 28 or 30 may be in the process of being engaged in a reverse gearratio of the DCT 18. In such a situation, the clutch 28 or 30 may ceaseto slip when the subject clutch locks up.

The controller 52 is also programmed to determine the amount of timeremaining until the clutch 28 or 30 will cease to slip using thedetermined vehicle parameters 54. In other words, the controller 52 maylook up the DCT upshift table 56 to determine when then the DCT 18 willexperience an upshift into another forward gear ratio. The controller 52is additionally programmed to determine an amount of time remaininguntil the clutch 28 or 30 reaches a threshold temperature 58. Thethreshold temperature 58 of the particular clutch 28 or 30 is indicativeof the clutch having absorbed sufficient thermal energy to be within apredetermined range of the above-described over-heat condition. Withinthe meaning of the present disclosure, the threshold temperature 58 maybe a value that corresponds to the clutch 28 or 30 having absorbedexcessive thermal loading. In one embodiment, the threshold temperature58 may be a temperature value that was previously assessed on or nearthe friction surface of the pressure plate 46 or the pressure plate 48.In another embodiment, the threshold temperature 58 may be a temperaturevalue that was previously assessed on or near the friction surface ofthe clutch facings 32-1 or 34-1. Such threshold temperature data maythen be assembled into a table to be programmed into the controller 52for subsequent access during operation of the DCT 18.

The controller 52 is additionally programmed to compare the determinedamount of time remaining until the clutch 28 or 30 will cease to slipwith the determined amount of time remaining until the subject clutchreaches the threshold temperature 58. Accordingly, such a comparisonwill facilitate a determination whether the subject clutch 28 or 30 ispredicted to cease slipping before the threshold temperature 58 has beenreached. Also, the controller 52 is programmed to activate an indicator60 if the determined amount of time remaining until the clutch 28 or 30reaches the threshold temperature 58 is less than the determined amountof time remaining until the subject clutch will cease to slip. Theindicator 60 may also be activated when the subject clutch 28 or 30substantially reaches the threshold temperature 58. The indicator 60 maybe an audible signal and/or a visual display. The visual display mayinclude a communicated request for an operator of the vehicle 10 to atleast one of i) increase speed or apply the vehicle brake 19, and ii)apply and hold the vehicle brake 19. The indicator may additionallyinclude a coded message stored in the controller 52 and configured to beretrieved on demand.

The controller 52 may also be configured to regulate operation of theDCT 18 such that energy input into the particular clutch 28 or 30 isreduced when the subject clutch substantially reaches the thresholdtemperature 58. Accordingly, the clutch 28 or 30 may be considered ashaving substantially reached the threshold temperature 58 if the clutchtemperature is within a predetermined temperature range of the thresholdtemperature. To thus reduce energy input to the particular clutch 28 or30, the controller 52 may disengage the subject clutch.

FIG. 3 depicts a method 70 of managing clutch thermal loads in the DCT18, as described above with respect to FIGS. 1-2. The method commencesin frame 72 with assessing via the controller 52 whether the vehicle 10is being accelerated by the engine 14. From frame 72, the methodproceeds to frame 74, where the method includes identifying via thecontroller 52 which clutch from the clutches 28 and 30 is being slippedduring the acceleration. From frame 74 the method moves on to frame 76.In frame 76 the method includes determining via the controller 52vehicle parameters 54 that, as described with respect to FIGS. 1-2, areindicative of the amount of time remaining until the clutch 28 or 30will cease to slip.

After frame 76, the method advances to frame 78 where the methodincludes determining via the controller 52 the amount of time remaininguntil the clutch 28 or 30 will cease to slip using the determinedvehicle parameters 54. Following frame 78 the method proceeds to frame80, where the method includes determining via the controller 52 theamount of time remaining until the clutch 28 or 30 reaches the thresholdtemperature 58. From frame 80 the method moves on to frame 82. In frame82 the method includes comparing via the controller 52 the determinedamount of time remaining until the clutch 28 or 30 will cease to slipwith the determined amount of time remaining until the subject clutchreaches the threshold temperature 58.

Furthermore, after frame 82, the method advances to frame 84 where themethod includes activating via the controller 52 the indicator 60 if thedetermined amount of time remaining until the clutch 28 or 30 reachesthe threshold temperature 58 is less than the determined amount of timeremaining until the subject clutch will cease to slip. Following frame84 the method may advance to frame 86 where it may additionally includeregulating via the controller 52 the operation of the DCT 18 such thatenergy input to the subject clutch 28 or 30 is reduced when the clutchsubstantially reaches the threshold temperature 58. Additionally, afterframe 84 the method may proceed to frame 88, where the method mayinclude activating via the controller 52 the indicator 60 when thesubject clutch 28 or 30 substantially reaches the threshold temperature58.

The described method is intended to facilitate increased durability andextended operating life for the DCT 18 and specifically of the clutches28 and 30 while also enhancing the user-friendliness of the DCT 18. Suchenhancement of the user-friendliness of the DCT 18 is achieved bypermitting the vehicle 10 to perform desired maneuvers withoutgenerating premature warnings as to an overloaded clutch or reducingperformance of the vehicle, if the clutch 28 or 30 that is being engagedand slipped will cease to slip prior to actually being overheated.

The detailed description and the drawings or figures are supportive anddescriptive of the invention, but the scope of the invention is definedsolely by the claims. While some of the best modes and other embodimentsfor carrying out the claimed invention have been described in detail,various alternative designs and embodiments exist for practicing theinvention defined in the appended claims.

The invention claimed is:
 1. A method of managing clutch thermal loadsin a multi-speed dual-clutch transmission (DCT) that is paired with aninternal combustion engine in a vehicle, the method comprising:assessing via a controller whether the vehicle is being accelerated bythe engine; identifying via the controller a clutch in the DCT that isbeing slipped during the acceleration; determining via the controllervehicle parameters indicative of a preset amount of time remaining untilthe clutch will cease to slip; accessing via the controller the presetamount of time remaining until the clutch will cease to slip thatcorresponds to the determined vehicle parameters; determining via thecontroller an actual amount of time remaining until the clutch beingslipped reaches a threshold temperature; comparing via the controllerthe accessed preset amount of time remaining until the clutch will ceaseto slip with the determined actual amount of time remaining until theclutch being slipped reaches the threshold temperature to determinewhether the clutch is predicted to cease slipping before the thresholdtemperature has been reached; and activating via the controller anindicator if the determined actual amount of time remaining until theclutch being slipped reaches the threshold temperature is less than theaccessed preset of time remaining until the clutch will cease to slip.2. The method of claim 1, wherein the threshold temperature isindicative of the clutch being overheated, the method further comprisingregulating an operation of the DCT such that energy input to the clutchis reduced when the clutch substantially reaches the thresholdtemperature.
 3. The method of claim 2, wherein said regulating theoperation of the DCT such that energy input to the clutch is reducedincludes disengaging the clutch.
 4. The method of claim 1, wherein theclutch is in the process of being engaged in a forward gear ratio of theDCT and the clutch ceases to slip upon an upshift to another forwardgear ratio using another clutch.
 5. The method of claim 4, wherein thedetermined vehicle parameters include road speed and acceleration of thevehicle, and position of a vehicle accelerator.
 6. The method of claim1, wherein the clutch is in the process of being engaged in a reversegear ratio of the DCT and the clutch ceases to slip upon lock up of theclutch.
 7. The method of claim 1, further comprising activating theindicator when the clutch substantially reaches the thresholdtemperature.
 8. The method of claim 1, wherein the indicator is at leastone of an audible signal and a visual display.
 9. The method of claim 8,wherein the indicator is the visual display, and wherein the visualdisplay includes a request for an operator of the vehicle to at leastone of i) increase speed or apply a vehicle brake, and ii) apply andhold the vehicle brake.
 10. The method of claim 1, wherein the clutch isone of an odd-ratio clutch and an even-ratio clutch.
 11. A vehiclecomprising: an internal combustion engine configured to generate enginetorque; a drive wheel configured to interface with a road surface; amulti-speed dual-clutch transmission (DCT) operatively connected to theengine and configured to transmit engine torque to the drive wheel; anda controller configured to: assess whether the vehicle is beingaccelerated by the engine; identify a clutch in the DCT that is beingslipped during the acceleration; determine vehicle parameters indicativeof a preset amount of time remaining until the clutch will cease toslip; access the preset amount of time remaining until the clutch willcease to slip that corresponds to the determined vehicle parameters;determine an actual amount of time remaining until the clutch beingslipped reaches a threshold temperature; compare the accessed amount oftime remaining until the clutch will cease to slip with the determinedactual amount of time remaining until the clutch being slipped reachesthe threshold temperature to determine whether the clutch is predictedto cease slipping before the threshold temperature has been reached; andactivate an indicator if the determined actual amount of time remaininguntil the clutch being slipped reaches the threshold temperature is lessthan the accessed amount of time remaining until the clutch will ceaseto slip.
 12. The vehicle of claim 11, wherein the threshold temperatureis indicative of the clutch being overheated, and wherein the controlleris additionally configured to regulate the operation of the DCT suchthat energy input to the clutch is reduced when the clutch substantiallyreaches the threshold temperature.
 13. The vehicle of claim 12, whereinthe controller regulates operation of the DCT such that energy input tothe clutch is reduced by disengaging the clutch.
 14. The vehicle ofclaim 11, wherein the clutch is in the process of being engaged in aforward gear ratio of the DCT and the clutch ceases to slip upon anupshift to another forward gear ratio using another clutch.
 15. Thevehicle of claim 14, wherein the determined vehicle parameters includeroad speed and acceleration of the vehicle, and position of a vehicleaccelerator.
 16. The vehicle of claim 11, wherein the clutch is in theprocess of being engaged in a reverse gear ratio of the DCT and theclutch ceases to slip upon lock up of the clutch.
 17. The vehicle ofclaim 11, wherein the controller is additionally configured to activatethe indicator when the clutch substantially reaches the thresholdtemperature.
 18. The vehicle of claim 11, wherein the indicator is atleast one of an audible signal and a visual display.
 19. The vehicle ofclaim 18, wherein the indicator is the visual display, and wherein thevisual display includes a request for an operator of the vehicle to atleast one of i) increase speed or apply a vehicle brake, and ii) applyand hold the vehicle brake.